The Litoria-Ewingi Complex (Anura, Hylidae) in South-Eastern Australia .9. Variation in Mitochondrial-Dna Across a Narrow Zone of Hybridization Between Litoria-Ewingi and Litoria-Paraewingi

Abstract

The mitochondrial DNA (mtDNA) of Litoria ewingi and L. paraewingi, two species of hylid frog occurring in south-eastern Australia, was investigated by restriction enzyme analysis. Clear diagnostic differences between allopatric populations of these two species were shown in several of the fragment patterns. MtDNA haplotypes of individuals from populations along a transect across the southern hybrid zone between L. ewingi and L. paraewingi were identified. Four individuals from these hybrid populations had inherited a unique haplotype of mtDNA. The width of the hybrid zone based on variation in mtDNA, is at least 5 km. The southern limit of introgression of mtDNA typical of L. paraewingi coincides with the southern limit based on call variation. However, mtDNA typical of L. ewingi was not found as far north as expected by other criteria. The relationship between mtDNA haplotype and structure of advertisement call in individuals from populations in the hybrid zone was analysed. The species-specificity of mtDNA established for allopatric populations held for all but two of the ten recorded putative parental males. Surprisingly, three of the four hybrids based on call structure had inherited mtDNA characteristic of L. ewingi.